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John J. O’Shea, M.D., is a Senior Investigator and Chief of the Molecular Immunology and Inflammation Branch of the National Institutes of Health National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). Dr. O’Shea is a leading inventor in the field of cytokine signal transduction, specifically in dissecting the role of the Janus kinases (JAKs) and signal transducers and activators of transcription (STATs) family transcription in immunoregulation. Dr. O'Shea discovered and cloned the tyrosine kinase, JAK3, which is essential for inducing the cascade of effects caused by immune system molecules called cytokines, including one known as interleukin-1 (IL-2), and demonstrated its role in pathogenesis of severe combined immunodeficiency. Dr. O'Shea identified the role of STAT3 in regulating T cell cytokine production in Job's syndrome. More recently, Dr. O’Shea’s laboratory has employed deep sequencing to understand the epigenetic regulation of T cell differentiation and the role of STATs in these processes. Dr. O'Shea was inducted as a Fellow of NAI in 2025.